Salesforce and Slack are once again aiming for Microsoft’s habit of bundling Teams with Office, arguing in a new UK lawsuit that the practice harms competition and limits customer choice.
Salesforce and Slack have been here before. Their long-running frustration with Microsoft’s bundling strategy has now escalated into a fresh legal battle in London’s High Court. According to Reuters reporting, Slack Technologies and related Salesforce entities filed the suit on April 23, saying they acted because Microsoft’s practices harmed competition by using tying and bundling of Teams to limit customer choice. A Slack spokesperson reiterated that the core issue is Microsoft forcing Teams into Office deals in ways that make it harder for rivals to compete on merit. Microsoft, unsurprisingly, disagrees. A spokesperson told Reuters the case lacks merit and argued Slack’s slower growth during the pandemic was due to inferior capabilities rather than any anticompetitive behavior.
This fight didn’t start in the UK. Slack first went to the European Commission in 2020, accusing Microsoft of bundling Teams with Office to gain an unfair advantage. That complaint eventually pushed Microsoft to offer Office packages without Teams at reduced prices, a move that helped the company avoid a potentially hefty fine. The new UK lawsuit suggests Salesforce and Slack believe those concessions didn’t go far enough, or at least didn’t address the structural advantage Microsoft maintains by tying its collaboration tools to its productivity suite.
Their argument hasn’t changed much since 2020, when Slack first told the European Commission that Microsoft had “created a weak, copycat product and tied it to their dominant Office product, force installing it and blocking its removal,” a complaint that triggered a multiyear investigation. Microsoft’s defense hasn’t changed much either. The company continues to insist that Teams succeeded because it was better, not because it was bundled, and that Slack’s slower growth was due to “inferior capabilities,” as Microsoft put it in comments highlighted by Reuters and echoed in recent coverage.
The EU case ultimately wrapped in 2025 with a deal that let Microsoft walk away without paying a fine. Regulators accepted Microsoft’s concessions, which included offering Office and Microsoft 365 without Teams at lower prices, widening the price gap by up to eight euros, and committing to improved interoperability and data portability for up to ten years. These remedies were enough for Brussels to declare the competition concerns addressed, but they didn’t fundamentally change Microsoft’s position in the market. Teams remained deeply entrenched, and the unbundled versions were still optional rather than the default.
That outcome is exactly why Salesforce and Slack are back in court, this time in the UK. Their new lawsuit argues that Microsoft’s structural advantage persists because bundling Teams with Office remains the norm, not the exception. The EU settlement may have opened the door to competition on paper, but Slack and Salesforce clearly believe it didn’t go far enough in practice. The UK case gives them another venue to push for stronger remedies, potentially ones that go beyond pricing tweaks and into rules that reshape how Microsoft can package its collaboration tools.
This fight also echoes Microsoft’s long history with bundling disputes. Regulators spent years wrestling with Windows and Internet Explorer, then Windows Media Player, and each time, Microsoft defended integration as innovation. Each time regulators pushed back, arguing that defaults can harden dominance in ways that rivals can’t overcome.
The timing of the lawsuit is also notable. It landed the same week London’s Competition Appeal Tribunal certified a separate mass claim accusing Microsoft of overcharging British businesses for using Windows Server software on rival cloud platforms. Microsoft disputes those allegations as well. When multiple cases surface in parallel, it reinforces a broader narrative that regulators and enterprise customers are increasingly skeptical of Microsoft’s market power and pricing strategies.
The outcome of this new UK case could shape how collaboration tools are packaged for years to come. If Salesforce and Slack prevail, Microsoft may face stricter rules on how Teams can be sold alongside Office. If Microsoft wins, it strengthens the company’s long-standing argument that bundling is simply part of building a cohesive ecosystem. Either way, the fight underscores how central workplace communication tools have become and how much is at stake when one company’s defaults become another company’s barriers.
